超重力熔铸铁基金属陶瓷材料多相运动学特征及其致密化机制

采用Fe_3O_4/Al/铁基硬质合金的铝热体系,超重力熔铸铁基金属陶瓷梯度材料,分析了超重力场中多相(硬质合金颗粒、Al_2O_3陶瓷相及气体相)在高热高温铁熔体内的运动学特征及其致密化机制。结果表明,根据Stocks定律,弥散相在高温熔体内的运动速度影响因素主要有颗粒与基体熔体密度差、超重力系数、颗粒半径及温度等,在一定的超重力系数下,材料的致密度与气泡尺寸、铁熔体存在时间有关。V-Fe和Cr-Fe 2种颗粒主要集中于金属陶瓷材料的顶端,沿超重力方向粒子尺寸逐渐减小,而Mo-Fe颗粒主要集中在金属陶瓷材料与45钢分界面处,不同颗粒在材料内的分布状况有较大差异,这是金属陶瓷材料硬度呈梯度变化的主要原因。     

电介质陶瓷材料辅助微波烧结金属铁粉压坯的试验研究

本文用氧化铝、碳化硅、氧化锆三种不同粒度的介质材料作为辅助材料,采用1 150℃、1 050℃两种烧结温度对铁基压坯材料进行微波烧结,获得不同物理性能、微观特征的铁坯,探讨不同介质材料对微波烧结的作用机理。结果表明,介质陶瓷材料对微波烧结金属铁基压坯有促进作用,其组织致密性、硬度明显高于无介质辅助加热。其辅助加热的作用是通过介质材料在微波加热过程中,由于存在介质损耗,介质分子间互相产生摩擦,引起介质温度升高,使介质材料内部、外部几乎同时加热升温,形成体热源状态,缩短了热传导时间,且物料内外加热均匀一致。介质材料影响由大到小依次是碳化硅、氧化锆和氧化铝,而粒度则影响不大。     

Hydrogen effect on thermodynamic stability of γ- and ε-phases in a Fe–Cr–Mn solid solution

Ab initio calculations of the cohesion energy in the fcc γ- and hcp ε-phases of the hydrogen-free and hydrogen-charged Fe50Cr25Mn25 solid solutions are carried out in order to estimate the hydrogen effect on the γ → ε transformation. It is obtained that, at hydrogen contents within the range of 20–35 at.%, the fcc and hcp structures reveal a comparable thermodynamic stability with some preference for the hcp one. With further increase in the hydrogen content, the fcc phase is again stabilized. The comparison with similar calculations for the Fe50Cr25Ni25 solid solutions shows that, in contrast to expectations, the substitution of nickel for manganese in the austenitic steels retards the hydrogen-induced γ → ε transformation. The obtained results are also compared with available experimental data and discussed in terms of stacking fault energy changed under combined hydrogen, nickel and manganese effects.     

A novel silicalite-1 zeolite shell encapsulated iron-based catalyst for controlling synthesis of light alkenes from syngas

A well-designed zeolite capsule catalyst with a Core (Fe/SiO₂)-Shell (Silicalite-1) structure was successfully prepared by zeolite seeding and then zeolite shell growing via secondary hydrothermal method. The characterization on this zeolite capsule catalyst indicated that it had a compact, defect-free zeolite shell enwrapping core catalyst tightly. The application of this zeolite capsule catalyst was the direct synthesis of light alkenes from syngas via Fischer–Tropsch synthesis (FTS) reaction. This zeolite capsule catalyst exhibited excellent abilities compared with the traditional FTS catalyst, both on the controlled synthesis of the desirable light alkenes and the suppressing formation of the undesired long-chain hydrocarbons.     

Removal of sulfur at high temperatures using iron-based sorbents supported on fine coal ash

This paper deals with the simultaneous removal of H₂S and COS in the temperature range of 400-650 °C at 1 bar by using iron-based sorbents. The iron-based sorbents were prepared using iron oxide and cerium oxide with coal fine ash as the support. Simulated coal gas was used in the sulfidation experiments and 5% O₂ in N₂ gas was used for regeneration of sorbents. Both sulfidation and regeneration experiments have been carried out using a fixed-bed quartz reactor. The product gases were analyzed using a GC equipped with a TCD and a FPD. The results demonstrated that both H₂S and COS can be effectively reduced using the iron-based sorbents supported on fine coal ash. XRD analysis shows that Fe_1−xS phase has formed during sulfidation indicating a high sulfur capacity of the sorbent. The mechanism of the removal of COS simultaneously with H₂S is also discussed.     

铁基激光熔覆层的开裂行为及开裂机理研究

本文通过研究铁基熔覆层裂纹的开裂形貌、扩展方向、裂纹源、断口特征等开裂行为探讨了其开裂机理.结果表明：熔覆层表面裂纹起源于熔覆层和基体结合处,垂直于焊道向表面扩展,且贯穿整个熔覆层表面,呈沿晶开裂特征;熔覆层中存在的孪晶,可提高熔覆层的塑性和韧性,降低了熔覆层的开裂倾向;熔覆层中的δ铁素体,可以增强熔覆层的抗热裂纹能力;开裂的熔覆层δ铁素体中存在大量体心立方结构的含Si复杂固溶体（C-Fe-Mn-Mo-Si）,且δ铁素体含量较少,是导致其韧性下降、裂纹出现的主要原因.     

费托合成沉淀铁催化剂性能的研究进展

费托合成（F-F合成）是实现煤间接液化技术的重要环节之一,其关键是开发高活性、选择性和稳定性的催化剂。目前应用的费托合成催化剂主要有铁基和钴基催化剂。铁基催化剂因价格低廉、催化活性和水煤气变换反应（WGS）活性高以及助剂效果明显,而在费托合成催化剂中占有重要的地位。本文对近几年铁基催化剂的特点和发展状况进行了评述,着重分析了催化剂制备过程、助剂和还原活化对其活性和选择性的影响。     

硫铁矿烧渣制备铁系化工产品研究

介绍了硫铁矿烧渣制取铁盐、铁系颜料、铁氧体材料、净水剂的工艺方法及国内外相关研究的进展.     

Comparative study of iron-based Fischer–Tropsch synthesis catalyst promoted with potassium or sodium

FeCu/SiO₂ catalysts, in which K or Na promoter is incorporated respectively, are prepared by a combination method of continuous co-precipitation and spray drying technology. The catalysts were characterized by temperature-programmed desorption and Mössbauer spectroscopy. The Fischer–Tropsch synthesis (FTS) performance of the catalysts was studied in a continuously stirred tank slurry reactor. The basicity of the K-promoted catalyst is enhanced, as demonstrated by CO₂-TPD results. MES results show that sodium can weaken the dispersion of α-Fe₂O₃ phase; either potassium or sodium can promote carburization of the catalyst, while the effect of sodium is weaker. FTS results indicate that the addition of K or Na can improve the catalyst activity, and shift the product distribution to heavy hydrocarbons to the different extent.     

Bulk glassy Fe-Cr-Mo-C-B alloys with high corrosion resistance

The preparation of bulk glassy alloys with high glass-forming ability and high corrosion resistance in Fe-based system was succeeded by means of copper-mold casting. The temperature interval of supercooled liquid region (ΔT_x) is as large as 53-62 K and the reduced glass transition temperature (T_g/T_m) is as high as 0.62-0.63 for the cast Fe_50−xCr₁₆Mo₁₆C₁₈B_x (x=4, 6, 8 at.%) glassy alloys. The corrosion rates of the Fe_50−xCr₁₆Mo₁₆C₁₈B_x glassy alloys with a diameter of 1.2 mm were in the range of 10⁻³-10⁻² mm year⁻¹ in 1, 6 and 12 N HCl solutions at 298 K. The bulk glassy alloys are spontaneously passivated in 1 and 6 N HCl solutions with wide passive region and low passive current density. They do not suffer pitting corrosion even when polarized anodicly in 12 N HCl solution up to 1.0 V (Ag/AgCl). The high corrosion resistance is due to the formation of chromium-rich passive films during immersion in HCl solutions. In addition, the increase of boron content in alloys improves the corrosion resistance of the bulk glassy alloys within the composition range examined.